Interação entre o óxido de grafeno e glifosato utilizando modelagem matemática e fluorescência molecular

Abstract

Emerging contaminants have been drawing the attention of many researchers, since they have several negative effects on human health and the environment in general. These pollutants are present in water used for public supply, irrigation of plantations and in different water bodies, reaching aquatic ecosystems. In Brazil, most of the economy comes from the primary sector (agriculture), being a country vast in diversity of crops and a major exporter of what it produces. Thus, there is a growing need for scale production, and it is in this context that agricultural pesticides are inserted. Glyphosate is a non-selective, systemic and post-emergent pesticide, representing 60% of the world herbicide market, and the most used in Brazil and in the state of Rio Grande do Sul. Inadequate handling and excessive use of pesticides cause changes in the fauna and flora in general, also causing air, water and soil contamination The difficulty of removing this chemical substance from water establishes the need for the development and use of techniques for treatment, among them, adsorption is the most used for this purpose. Thus, carbon-based materials stand out as an option for removing contaminants from water bodies, among them, graphene oxide (GO) is the one that most draws attention to this function, due to its unique properties and its functional groups, mainly oxygenates. According to the literature found, GO demonstrates efficiency in removing pollutants from water. However, what the works do not show is how the interaction with the contaminant occurs, based on this, the purpose of this work is to demonstrate how GO and glyphosate interact, for which the molecular fluorescence technique will be used combined with mathematical modeling. The first stage of the work consisted of synthesizing three different types of GO, and evaluating their fluorescence. Sequentially, experimental optimization and analyzes between GO's and glyphosate were performed. After analyzing all the results obtained with the experiments carried out throughout the work, it is possible to say that the synthesis of route 1 of graphene oxide was successfully performed, so that the functional groups of the material are possible. Fluorescence quenching was analyzed using predefined additions of glyphosate. For the analysis, the wavelength at which GO presented the highest intensity peak was used. Therefore, the results demonstrated that GO1 presented a gradual attenuation in the intensity values while in the two other routes, the intensity did not vary significantly when in contact with the contaminant. This is possibly due to having a smaller amount of carboxylic groups, glyphosate has nowhere to bind to create stability and thus decrease the intensity. Finally, through the adapted Stern-Volmer mathematical model, it was possible to prove that 5 the binding of GO1 with glyphosate is of an intermediate strength, being considered a stable interaction with energy large enough to retain the contaminant.